Leaving abortion up to the individual states is untenable

It is untenable for the very same reason that the Fugitive Slave Act was ultimately untenable: because it raises questions about the obligations under the full faith and credit clause of the Constitution of states where abortion is legal to those states where it is not. You simply cannot have a situation where something is treated as a major crime in one state while being perfectly legal in another. Republicans who try to make this claim are attempting to claim a "middle ground" that does not, in fact, exist!